<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="../js/form.js"></script>
</head>
<body>
<input type="text" id="username">
<div id="result"></div>
<input type="button" value="判断" onclick="reg()">
</body>
</html>